In recent years, renewable energy has been increasingly introduced in an electric power field, and as a measure for system stabilization, introduction or enhancement of power electronics equipment such as a STATCOM (static synchronous compensator) is performed. In the power electronics equipment, a voltage converter is needed, and in the voltage converter, a semiconductor such as an IGBT is used as a switch for current. In the converter, a bypass switch is needed for protecting a diode or preventing breakdown of the system upon failure of the IGBT. The bypass switch is to protect the diode or prevent breakdown of the system by short-circuiting and closing the bypass switch itself upon failure of the IGBT. Therefore, the bypass switch needs to operate before the diode fails. However, since the time until the diode fails is very short, it is important, as a required function of the bypass switch, that the time until closing since reception of a signal is as short as possible.
The bypass switch used in the power electronics equipment is required to allow high voltage or large current to be applied by means of short-circuit closing. Therefore, a vacuum valve may be employed for a switch main unit.
An example of conventional operation mechanism units for the vacuum valve includes: an open/close rod connected to a movable contact of the vacuum valve; an open/close block which is provided to the open/close rod, movable in the axial direction, and engaged via a predetermined play; and a disk-like open/close spring which is displaced in accordance with movement of the open/close block and has a greater turnover load to the open/close block than a vacuum-self-closing force of the vacuum valve, wherein the open/close block is moved in the axial direction by an operation lever, whereby the open/close spring acts in a contact-opening or contact-closing direction to perform contact opening or contact closing (for example, see Patent Document 1).